Shaped article from unbleached pulp and the process

ABSTRACT

In accordance with the present invention, lyocell products can be made with unbleached pulps resulting in products with high amounts of hemicellulose and high amounts of lignin as compared to conventional lyocell products. The lyocell products of the present invention are advantageously less expensive to produce but retain the desirable strength of conventional lyocell products.

FIELD OF THE INVENTION

[0001] The present invention is directed to products made fromunbleached pulps, the process used to make such products and theprocesses used to make cellulose solutions from unbleached pulp forspinning into lyocell products.

BACKGROUND OF THE INVENTION

[0002] Cellulose is a polymer of D-glucose and is a structural componentof plant cell walls. Cellulose is especially abundant in tree trunksfrom which it is extracted, converted into pulp, and thereafter utilizedto manufacture a variety of products. Rayon is the name given to afibrous form of regenerated cellulose that is extensively used in thetextile industry to manufacture articles of clothing. For over acentury, strong fibers of rayon have been produced by the viscose andcuprammonium processes. The latter process was first patented in 1890and the viscose process two years later. In the viscose process,cellulose is first steeped in a mercerizing strength caustic sodasolution to form an alkali cellulose. The cellulose is then reacted withcarbon disulfide to form cellulose xanthate, which is then dissolved ina dilute caustic soda solution. After filtration and deaeration, thexanthate solution is extruded from submerged spinnerets into aregenerating bath of sulfuric acid, sodium sulfate, zinc sulfate, andglucose to form continuous filaments. The resulting viscose rayon ispresently used in textiles and was formerly widely used for reinforcingrubber articles such as tires and drive belts.

[0003] Cellulose is also soluble in a solution of ammonia copper oxide.This property forms the basis for the production of cuprammonium rayon.The cellulose solution is forced through submerged spinnerets into asolution of 5% caustic soda or dilute sulfuric acid to form the fibers,which are then decoppered and washed. Cuprammonium rayon is available infibers of very low deniers and is used almost exclusively in textiles.

[0004] The foregoing processes for preparing rayon both require that thecellulose be chemically derivatized or complexed in order to render itsoluble and therefore capable of being spun into fibers. In the viscoseprocess, the cellulose is derivatized, while in the cuprammonium rayonprocess, the cellulose is complexed. In either process, the derivatizedor complexed cellulose must be regenerated and the reagents used tosolubilize it must be removed. The derivatization and regeneration stepsin the production of rayon significantly add to the cost of this form ofcellulose fiber. Consequently, in recent years attempts have been madeto identify solvents that are capable of dissolving underivatizedcellulose to form a dope of cellulose from which fibers can be spun.

[0005] One class of organic solvents useful for dissolving cellulose arethe amine N-oxides, in particular the tertiary amine N-oxides. Forexample, Graenacher, in U.S. Pat. No. 2,179,181, discloses a group ofamine oxide materials suitable as solvents. Johnson, in U.S. Pat. No.3,447,939, describes the use of anhydrous N-methylmorpholine-N-oxide(NMMO) and other amine N-oxides as solvents for cellulose and many othernatural and synthetic polymers. Franks et al., in U.S. Pat. Nos.4,145,532 and 4,196,282, deal with the difficulties of dissolvingcellulose in amine oxide solvents and of achieving higher concentrationsof cellulose.

[0006] Lyocell is an accepted generic term for a cellulose fiberprecipitated from an organic solution in which no substitution ofhydroxyl groups takes place and no chemical intermediates are formed.Several manufacturers presently produce lyocell fibers, principally foruse in the textile industry. For example, Acordis, Ltd. presentlymanufactures and sells a lyocell fiber called Tencel® fiber.

[0007] Currently available lyocell fibers are produced from wood pulpsthat have been extensively processed to remove non-cellulose components,especially hemicellulose, and lignin. These highly processed pulps arereferred to as high alpha (or high α) pulps, where the term alpha (or α)refers to the percentage of cellulose. Thus, a high alpha pulp containsa high percentage of cellulose, and a correspondingly low percentage ofother components, especially hemicellulose and lignin. The processingrequired to generate a high alpha, low lignin pulp significantly adds tothe cost of lyocell fibers and products manufactured therefrom.

[0008] Furthermore, the wood chips are pretreated with an acid beforethe pulping stage, since it is not possible to obtain acceptable highalpha pulps for lyocell products otherwise through the Kraft process. Asignificant amount of material, primarily hemicellulose on the order of10% or greater, of the original wood substance is solubilized in thisacid phase pretreatment. Thus process yields are significantlydiminished. Omitting the acid phase pretreatment will result in a highhemicellulose pulp. The disadvantage of conventional high alpha pulps isthe reduction of yield by eliminating hemicelluloses from the pulp.

[0009] Conventional high alpha pulps are also bleached. Bleaching refersto the removal of lignin in a process subsequent to the pulping process.Removing lignin also reduces the overall yield of the original woodmaterial.

[0010] In view of the expense of producing lyocell products from highalpha pulps that have small amounts of hemicellulose and lignin, itwould be desirable to have alternatives to high alpha, low lignin pulpsfor making lyocell products.

[0011] Thus there is a need for relatively inexpensive, low alpha, highyield, high hemicellulose, and high lignin pulps that are useful formaking lyocell products.

[0012] In U.S. Pat. No. 6,210,801, fully incorporated herein byreference in its entirety, high hemicellulose containing pulp isdescribed that is useful for lyocell products. The pulp is made byreducing the viscosity of the cellulose without substantially reducingthe hemicellulose content, followed by reducing the copper number.

[0013] While the methods described in the '801 patent are effective atreducing the viscosity of cellulose without substantially decreasing thehemicellulose content, a further need existed for a process that did notrequire a separate copper number reducing step, and that was readilyadaptable to pulp mills that have oxygen reactors. In U.S. Pat. No.6,331,354, fully incorporated herein by reference in its entirety, ahigh hemicellulose, low viscosity pulp is described that is useful formaking lyocell products that does not require an additional coppernumber reducing step. The pulp is made from an alkaline pulp by treatingthe alkaline pulp with an oxidizing agent in a medium to highconsistency oxygen reactor to reduce the viscosity of the cellulose,without substantially reducing the hemicellulose or increasing thecopper number of the pulp. Further efforts to reduce the cost of makinglyocell products are described in U.S. application Ser. No. 09/842,274,fully incorporated herein by reference in its entirety. In the '274application, the pulps are made from sawdust and other low length fiberwood. These pulps are high in hemicellulose and low in viscosity, andare composed of short fibers suitable for producing lyocell products.

[0014] However, until now, all of the prior art dissolving pulps forproducing lyocell products are low in lignin content. It would beadvantageous to develop a high lignin pulp that is useful for makinglyocell products as an alternative to the highly refined low yield highalpha pulps.

SUMMARY OF THE INVENTION

[0015] In accordance with the present invention, lyocell products can bemade with unbleached pulps resulting in products with high amounts ofhemicellulose and high amounts of lignin as compared to conventionallyocell products. The lyocell products of the present invention areadvantageously less expensive to produce but retain the desirablestrength of conventional lyocell products.

[0016] One embodiment of the invention provides a high hemicellulose,high lignin lyocell fiber. The fiber has a dry tenacity of at least 46cN/tex at a gauge length of about 10 mm and a dry tenacity of at least30 cN/tex at a gauge length of about 30 mm. The hemicellulose content ofthe fiber is at least 7% and the lignin content of the fiber is at least2% measured as Klason lignin.

[0017] In another embodiment of the invention, a lyocell fiber has anaverage diameter of from 9 to 16 microns; however, other embodiments offibers have an average diameter of from 12 to 14 microns.

[0018] In another embodiment of the invention, a method for making alyocell product is described. The method includes modifying a pulphaving at least 7% hemicellulose and at least 2% Klason lignin by acidhydrolysis to lower the average degree of polymerization of thecellulose in the pulp, wherein greater than 95% of cellulose has anaverage D.P. from greater than about 400 to about 1100. The method alsoincludes dissolving the unbleached pulp in a solvent to provide acellulose solution, and spinning the cellulose solution into a lyocellproduct. The method uses meltblowing, centrifugal spinning,spun-bonding, or dry-jet wet spinning techniques. Fibers, films, andself-bonded nonwoven webs from unbleached pulps can be producedaccording to the methods of the invention.

[0019] In another embodiment of the invention, a pulp is provided. Thepulp has at least 7% hemicellulose and at least 2% Klason lignin. Thepulp also has cellulose, wherein greater than 95% of the cellulose hasan average D.P. of from greater than about 400 to about 1100.

[0020] In another embodiment of the invention, a meltblowing method formaking a lyocell product is provided. The method includes extruding acellulose solution of unbleached pulp through a plurality of aperturesto produce continuous cellulose filaments. The method includesstretching the filaments with air.

[0021] According to the present invention, an unbleached pulp, havingbeen modified to reduce its average degree of polymerization ofcellulose, results in substantial increases in yield. The high amountsof hemicellulose and lignin contribute to this greater improvement inoverall yield. This advantage, along with numerous related advantages,makes the lyocell product of this invention more desirable in comparisonwith previous technology.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 shows a block diagram of one embodiment of a methodaccording to the present invention;

[0023]FIG. 2 shows a block diagram of one embodiment of a methodaccording to the present invention;

[0024]FIG. 3 shows an illustration of a system for carrying out thepresent invention;

[0025]FIG. 4 shows an illustration of a system for carrying out thepresent invention;

[0026]FIG. 5 is a scanning electron micrograph of commercial lyocellfibers produced by a dry-jet wet spinning method;

[0027]FIG. 6 is a scanning electron micrograph of commercial lyocellfibers produced by a dry-jet wet spinning method;

[0028]FIG. 7 is a scanning electron micrograph of a lyocell fiberproduced from modified unbleached pulp according to the presentinvention;

[0029]FIG. 8 is a scanning electron micrograph of a self-bonded lyocellnonwoven web made by a meltblown spinning method from modifiedunbleached pulp according to the present invention;

[0030]FIG. 9 is a scanning electron micrograph of a self-bonded lyocellnonwoven web made by a meltblown spinning method from modifiedunbleached pulp according to the present invention;

[0031]FIG. 10 is a scanning electron micrograph of a self-bonded lyocellnonwoven web made by a meltblown spinning method from modifiedunbleached pulp according to the present invention.

[0032]FIG. 11 is a graphical illustration of diameter distribution formeltblown lyocell fibers made from modified unbleached pulp according tothe present invention; and

[0033]FIG. 12 is a graphical illustration of diameter distribution fordry-wet jet lyocell fibers made from modified unbleached pulp accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] Referring to FIG. 1, one embodiment of a method of making lyocellproducts from high hemicellulose, high lignin pulp is illustrated. Inblock 100, Kraft pulp or any other suitable alkaline pulp is obtainedfrom any adequate supplier, such as from the Weyerhaeuser Company. InKraft and alkaline pulping, the active chemical compounds are NaOH andNa₂S. Other chemicals may be added to influence or impart desirableeffects during the pulping process. These additional chemicals are wellknown to those skilled in the art. According to the present process, thewood does not undergo an acid phase pre-treatment step as has been theconventional practice of making dissolving pulp for lyocell products.Rather, the wood is pulped according to conventional methods. The Kraftor alkaline pulping process usually ends with washing the brownstockpulp. Alternatively, one embodiment of the invention can omit thepulping step, block 100, in favor of obtaining a suitable unbleachedpulp from suppliers of unbleached pulp. One suitable supplier is theWeyerhaeuser Company.

[0035] Conventional dissolving pulps for lyocell products are processedthrough a sequence of bleaching towers to reduce the lignin content.However, in the present invention, the bleaching stages are omitted. Instep 102, the unbleached pulp is modified to reduce its viscosity.Reducing the viscosity of the pulp increases its ability to dissolve.The viscosity of the unbleached pulp is reduced so that the average D.P.of 95% of the cellulose is modified to greater than 400 to about 1100.Unbleached pulps are made into lyocell products by first dissolving theunbleached pulp in an amine oxide and then spinning the solution intofilaments followed by regeneration of the filaments. One method formodifying the viscosity of unbleached pulp is by acid hydrolysis. Anyacid may be utilized, such as hydrochloric acid or sulfuric acid. Theacid may be utilized in the form of a liquid, or may be formed from agas, such as by dissolving hydrogen chloride gas in an aqueous medium.Another method is by swelling the cellulose in an alkaline solutionfollowed by alkali removal and treatment with a cellulolytic enzyme,preferably an endogluconase enzyme. Alternatively, steam explosion canbe utilized. Further, any combination of methods for viscosity reductioncan be utilized, such as steam explosion combined with acid hydrolysis.An advantage of utilizing acid hydrolysis to reduce viscosity is thattransition metal contaminants in the pulp are removed by the acidtreatment. If an acid treatment step is not utilized, then analternative method of removing transition metals from the pulp can beutilized, such as treatment of the pulp with a chelating agent. Otherequally suitable methods for reducing the viscosity of unbleached pulpsare described in the aforementioned U.S. Pat. Nos. 6,210,801 and6,331,354, fully incorporated herein by reference in their entirety.

[0036] Unbleached pulps having their viscosity modified can be spun intolyocell products. Modified unbleached pulps are high in hemicelluloseand high in lignin and can readily dissolve to provide cellulosesolutions that can be spun into lyocell products.

[0037] Methods for measuring pulp viscosity are well known in the art,such as TAPPI T230. Methods used for measuring hemicellulose include,for example, a sugar content assay based on TAPPI standard T29 hm-85.Methods for expressing lignin content are also well known. The amount oflignin can be expressed as Kappa number, Klason lignin, or K(permanganate) number.

[0038] Following the pulping process, block 100, or the viscosityreduction process, block 102, the brownstock pulp can be made into aform which is suitable to be transported or stored, or otherwisetransformed into a more convenient form for handling. A pulp may beprovided in a roll, sheet, or bale, for example.

[0039] Referring still to FIG. 1, to make lyocell products from themodified, unbleached pulp, the pulp can be washed in water andtransferred to a bath of organic solvent for dissolution, preferably atertiary amine oxide, block 104. Representative examples of amine oxidesolvents useful in the practice of the present invention are set forthin U.S. Pat. No. 5,409,532, fully incorporated herein by reference inits entirety. The preferred amine oxide solvent isN-methyl-morpholine-N-oxide (NMMO). Other representative examples ofsolvents useful in the practice of the present invention includedimethylsulfoxide (D.M.S.O.), dimethylacetamide (D.M.A.C.),dimethylformamide (D.M.F.) and caprolactan derivatives. The pulp isdissolved in amine oxide solvent by any known method such as set forthin U.S. Pat. Nos. 5,534,113; 5,330,567; and 4,246,221, fullyincorporated herein by reference in their entirety. The pulp solution iscalled “dope.” The dope can be used to manufacture lyocell fibers,films, and nonwovens or other products by a variety of techniques,generally referred to as spinning, block 106. Spinning includes methodssuch as meltblowing, spun-bonding, centrifugal spinning, dry-jet wet,and other equally suitable methods. Some of these techniques are morefully described in U.S. Pat. Nos. 6,235,392; 6,306,334; 6,210,802; and6,331,354, fully incorporated herein by reference in their entirety.Examples of techniques for making films are set forth in U.S. Pat. Nos.5,401,447; and 5,277,857, fully incorporated herein by reference intheir entirety. Spinning results in a lyocell product, block 108, of thepresent invention, wherein the lyocell product has a high hemicellulosecontent, and a high lignin content, but is suitable to use asalternatives to conventional lyocell products, including fibers, films,or nonwovens, for example.

[0040] One embodiment of a method for making lyocell fibers from dopederived from modified unbleached pulp having high hemicellulose and highlignin involves extruding the dope through a die to form a plurality offilaments, followed by washing the filaments to remove the solvent, andthen drying the lyocell filaments. FIG. 2 shows a block diagram of oneembodiment of a method for forming lyocell fibers from a modified,unbleached pulp having high hemicellulose and high lignin contentaccording to the present invention. Starting with high hemicellulose,high lignin pulp in block 200, the pulp is physically broken down, forexample, by a shredder in block 202. The pulp is dissolved with an amineoxide-water mixture to form a dope, block 204. The pulp is wet with anonsolvent mixture of about 40% NMMO and 60% water. The mixture can bemixed in a double arm sigma blade mixer and sufficient water distilledoff to leave about 12-14% based on NMMO so that a cellulose solution isformed, blocks 206 and 208. Alternatively, NMMO of appropriate watercontent may be used to eliminate the need for the water removal step208. This is a convenient way to prepare spinning dopes in thelaboratory where commercially available NMMO of about 40-60%concentration can be mixed with laboratory reagent NMMO having onlyabout 3% water to produce a cellulose solvent having 7-15% water.Moisture normally present in the pulp should be accounted for inadjusting the water present in the solvent. Reference is made toarticles by Chanzy, H., and A. Peguy, Journal of Polymer Science,Polymer Physics Ed. 18:1137-1144 (1980), and Navard, P., and J. M.Haudin, British Polymer Journal, December 1980, p. 174, for laboratorypreparation of cellulose dopes in NMMO and water solvents.

[0041] The cellulose solution derived from the modified, unbleached pulpdope is forced through extrusion orifices in a process called spinning,block 210, to produce cellulose filaments that are then regenerated witha non-solvent, block 212. Finally, the lyocell filaments or fibers canbe washed and dried, block 214. Filaments may also be aggregated into anonwoven web before regeneration.

[0042] In meltblowing, the cellulose solution is forced from extrusionorifices into a turbulent airstream. Meltblowing produces continuouscellulose filaments and causes stretching of the filaments with the air.Where the fibers are produced by centrifugal spinning, the cellulosesolution is fed to a rotating head and expelled through small orificesinto air. The cellulose filaments are drawn or stretched by theresistance of the air caused by the rapidly rotating head. Inmeltblowing and centrifugal spinning, the latent filaments areregenerated in a bath or with sprayers. In other embodiments,conventional processes for forming lyocell fibers can be used whichcontinuously mechanically pull the extruded filaments linearly downwardinto a regenerating bath through an air gap. The latter process issometimes referred to as a “dry-jet wet” spinning process.

[0043] In the dry-jet wet spinning process, cellulose solution isextruded from a multiplicity of fine apertured spinnerets into an airgap. The filaments of cellulose dope are continuously mechanicallydrawn. They are then led into a nonsolvent, usually water, to regeneratethe cellulose. Examples of this process are described in McCorsley inU.S. Pat. Nos. 4,142,913; 4,144,080; 4,211,574; 4,246,221; and others.These patents are expressly incorporated herein by reference in theirentirety.

[0044] More specifically, in meltblowing, a supply of dope is pumpedthrough an extrusion head having a multiplicity of orifices. Compressedair or any other suitable gas is supplied to the extrusion head. Latentcellulose filaments are extruded from the orifices. These thin strandsof cellulose solution are picked up by the high velocity gas streamexiting from the orifices and are stretched or elongated by the gas. Thelatent filament strands can be regenerated by passing between spraypipes that carry water or any other suitable regenerating liquid.Alternatively, the strands can pass into a regenerating bath. Theregenerated filaments are then picked up by a rotating pickup roll wherethey accumulate until a sufficient amount of fiber has accumulated.

[0045] In centrifugal spinning, the cellulose solution is directed intoa hollow cylinder or drum with a base and a multiplicity of smallapertures in the sidewalls. As the cylinder rotates, cellulose solutionis forced out horizontally through the apertures as thin cellulosefilaments or strands. As these strands meet resistance from thesurrounding air, they are drawn or stretched. The cellulose strands willfall by gravity or are gently forced downward by an air flow into anon-solvent where they coagulate into individual oriented fibers.

[0046] Processes for meltblowing cellulose solutions are described inU.S. Pat. Nos. 6,235,392 and 6,306,334, incorporated herein by referencein their entirety. The centrifugal spinning method is described in U.S.Pat. No. 6,235,392.

[0047] In meltblowing, centrifugal spinning, and spun-bonding, as thecellulose filaments encounter resistance from the air, they will bedrawn or stretched by contact with the air. The cellulose filaments willalso undergo a reduction in diameter. The amount of stretching willdepend on readily controllable factors such as orifice size, dopeviscosity, cellulose concentration in the dope, air speed, nozzlediameter, spinning temperature, winder speed, bath temperature, etc.Meltblowing and centrifugal spinning can be used to produce nonwovenwebs, as described in U.S. Pat. No. 6,235,392.

[0048] One particularly useful embodiment of an apparatus for making alyocell nonwoven web made from an aggregate of lyocell fibers is shownin U.S. Pat. No. 6,235,392. However, in the present invention, thecellulose material is provided from a modified unbleached pulp havinghigh hemicellulose and high lignin. Referring to FIG. 3, a cellulosedope is pumped via line 300 to an extruder 302 and from there to anextrusion head 304. An air supply source 306 stretches the dope strands308 as they descend from the extrusion head. Process parameters arepreferably chosen so that the resulting cellulose fibers will becontinuous rather than random shorter lengths. The fibers fall onto anendless moving foraminous belt 310 supported and driven by rollers 312and 314. Here they form a latent nonwoven fabric mat 316. A top roller,not shown, may be used to press the fibers into tight contact and ensurebonding at the inter-fiber crossover points. As the mat 316 proceedsalong its path while supported on belt 310, a regenerating solution,including water, is sprayed downward by sprayer 318. The regeneratedproduct 322 is then removed from the end of the belt where it may befurther processed, for example, by washing, and drying.

[0049]FIG. 4 shows an alternative embodiment of an apparatus for makinga lyocell self-bonded nonwoven web made from an aggregate of lyocellfibers using centrifugal spinning. Referring to FIG. 4, cellulose dope400 is fed into a rapidly rotating drum 402 having a multiplicity oforifices 404 in the sidewalls. Latent fibers 406 are expelled throughorifices 404 and drawn, or lengthened by air resistance and the inertiaimparted by the rotating drum 402. They impinge on the inner sidewallsof a receiver surface 408 concentrically located around the drum. Thereceiver 408 may optionally have a frustroconical lower portion 410. Acurtain or spray of regenerating solution, including water, supplied vialine 412 flows downward from ring 414 located around the walls of thereceiver 408 to partially coagulate the cellulose mat that impinges onthe sidewalls of the receiver 408. Ring 414 may be located as shown inFIG. 4 or moved to a lower position if more time is needed for thelatent fibers to self-bond into a nonwoven web. The partially coagulatednonwoven web 416 is pulled from the lower part 410 of the receiver intoa coagulating bath 418 in container 420. As the web moves along itspath, it is collapsed from a cylindrical configuration into a planartwo-ply nonwoven structure. The web is held within the bath as it movesunder rollers 422, 424. A take-out roller 426 removes the now fullycoagulated 2-ply web 428 from the bath. Any or all of rollers 422, 424,or 426 may be driven. The web 428 is then continuously directed into awash and/or bleaching operation, not shown, following which it is driedfor storage. It may be split and opened into a single ply nonwoven, ormaintained as a 2-ply material as desired.

[0050] As can be seen from FIGS. 5 and 6, the morphology of themeltblown lyocell fibers from the modified unbeached pulps have uniqueproperties. The dry-jet wet lyocell fibers usually have smooth surfacesand a consistent cross-sectional diameter. The dry-jet wet lyocellfibers do not have crimps that are produced by the spinning method.Meltblown lyocell fibers regularly have pebbled surfaces. Meltblownlyocell fibers vary in cross-sectional diameter along the length of thefiber and have crimps due to the meltblowing process. The meltblownlyocell fibers have greater diameter variability along the fiber lengthand between fiber to fiber as compared with fibers produced from adry-jet wet method. Many of the characterizing morphological features ofmeltblown lyocell fibers are described in U.S. Pat. No. 6,235,392.

[0051] Microfibers can be produced by the meltblowing spinning process;however, self-bonded nonwoven webs using the meltblown process is alsoof great commercial interest. Self-bonded meltblown nonwoven webs madefrom modified unbleached pulp are produced. Referring now to FIGS. 8-10,some distinguishing features of the nonwoven webs made from meltblowingthe modified unbleached Kraft pulp are shown. It is apparent that thefiber segments in the nonwoven web made from unbleached modified Kraftpulp have similar features as the meltblown lyocell fiber described inearlier patents. However, in the present application, the nonwoven websare produced from modified unbleached pulps having high hemicelluloseand high lignin content, and accordingly, have a lower brightnessmeasurement. The morphological features of the fibers can have distinctadvantages for particular applications. The lyocell fibers in thenonwoven web structure were regularly bonded at the cross points. Thenonwoven web structure appears to be very porous. By adjusting theprocessing conditions, self-bonded nonwoven webs of different basisweights can be produced and the tensile properties of the nonwoven webstructure can be optimized for specific applications. In FIGS. 9 and 10,the bonded areas are shown in great detail and more than two fibers arebonded together at one crossover point. This will impart additionalstrength to the nonwoven web structure.

[0052] Lyocell fibers produced by meltblowing, centrifugally spinning,or spun-bonding modified, unbleached cellulose pulps possess a naturalcrimp quite unlike that imparted by a conventional stuffer box. Crimpimparted by a stuffer box is relatively regular, has a relatively lowamplitude, usually less than a 1 fiber diameter, and a shortpeak-to-peak period, normally not more than 2 or 3 fiber diameters. Thefibers made according to the present invention have an irregularamplitude greater than 1 fiber diameter, usually much greater, and anirregular period exceeding about 5 fiber diameters, a characteristic offibers having a curly or wavy appearance. The fiber diameter along thelength of each individual fiber can vary, as well as the average fiberdiameter between fibers. A quantifiable measurement of this variabilityis termed coefficient of variability. The fibers of the presentinvention have a range of diameters and tend to be somewhat curly givingthem a natural crimp. This natural crimp is quite unlike the regularsinuous configuration obtained in a stuffer box. Both amplitude andperiod are irregular and are at least several fiber diameters in heightand length. Most of the fibers are somewhat flattened and some show asignificant amount of twist. The methods are useful in producingmicrofibers. In one embodiment, average fiber diameter varies from about6 to 42 microns. In one embodiment, average fiber diameter is about 9 to16 microns. In one other embodiment, average fiber diameter is about12-14 microns.

[0053] Lyocell products, including fibers, films, and nonwovens madefrom modified unbleached pulp having high hemicellulose and high lignincontent are high in tenacity regardless whether they are made frommeltblowing, centrifugal spinning, spun-bonding, dry-jet wet or anyother method. Modified, unbleached pulps having high hemicellulose andhigh lignin can also be made into microfibers having an average size ofabout 0.1 denier.

[0054] In one embodiment, a lyocell fiber was made from modifiedunbleached pulp having high hemicellulose, and high lignin. The lignincontent of the fiber was at least 2% Klason lignin. The hemicellulosecontent of the fiber was at least about 7%. The lyocell fiber furthercontains cellulose, wherein greater than 95% of the cellulose has anaverage D.P. of from greater than 400 to 1100. The lyocell fiber has adry tenacity of at least 46 cN/tex at a gauge length of about 10 mm or adry tenacity of at least 30 cN/tex at a gauge length of about 30 mm. Theaverage diameter of the fiber can range from about 6 to about 19 micronsusing a dry-jet wet process to about 2 to about 46 microns using ameltblowing process. The median appears to lie between about 9 to about16 microns, or between about 12 to about 14 microns.

[0055] Using the dry jet wet spinning process, lyocell fibers producedfrom modified unbleached Kraft pulp having high hemicellulose and highlignin content were produced having the diameter distribution shown inFIG. 11. In one embodiment, the average diameter of a dry-jet wetlyocell fiber made from modified unbleached Kraft pulp is about 12microns, and the fibers have denier of about 1.3.

[0056] Using the meltblowing spinning method, lyocell fibers producedfrom modified unbleached Kraft pulp having high hemicellulose and highlignin content were produced having the diameter distribution shown inFIG. 12. Fiber diameter measurement was made using an opticalmicroscope. About 200 fibers were randomly chosen from each sample formeasurement. Average diameter and coefficient of variability werecalculated. Coefficient of variability is described in U.S. Pat. No.6,331,354, expressly incorporated herein by reference in its entirety.

[0057] A scanning electron microscope (SEM) or an optical microscope wasused to observe the morphology of the fibers or the nonwoven web.

[0058] The mechanical properties of the fibers produced by the dry-jetwet method was measured with an Instron tester. Measurement of fiberbundles of 10 filaments was used to determine the average.

[0059] The following examples now merely illustrate the best mode nowcontemplated for practicing the invention, but should not be construedto limit the invention.

EXAMPLE 1 Dry-Jet Wet and Meltblown Spinning Process Condition

[0060] Lyocell fibers were produced using laboratory process equipmentfrom both the Thuringisches Institut Fur Textil Und Kunststoff-Forschung(TITK) and the Weyerhaeuser Technology Center (WTC). Table 1 illustratessome of the process conditions used for the dry-jet wet and meltblowingmethods. TABLE 1 TITK lab WTC lab process process WTC Basic condition(DJW) (DJW) meltblown Nozzle diameter 75-90 80 450 (micron) Spinningtemperature 85-90 90-105 90-105 ° C. Winder speed (m/m)  70-10060-100 >200 Bath temperature 4-5 20-30  20-30  ° C. (water/NMMO (water)(water) mixture)

[0061] It was found that the average diameter of the TITK dry-jet wetlyocell fibers from modified unbleached Kraft is about 12 microns, andthe fibers have a denier of about 1.3. The diameter distribution isshown in FIG. 11. As can be seen from FIG. 11, the diameter of thedry-jet wet lyocell fibers from the modified unbleached Kraft pulps hadsome variability. The variability may have contributed to tenacityvariability as discussed below.

EXAMPLE 2 Mechanical Properties of the Dry-Jet Wet Lyocell Fibers

[0062] An Instron tester was used to measure the mechanical propertiesof the dry-jet wet lyocell fibers. The properties are shown in Table 2.TABLE 2 Tensile Tensile at Elongation Energy Tensile at Max. Load atMax. Absorption Max. Load MOE Width (kgf) Load (%) (J/m{circumflex over( )}2) (kN/m) (GPa) (mm) 30 MM GAUGE LENGTH 0.048 7.44 2147 29.36 40.990.016 0.028 8.58 1774 24.77 29.44 0.011 0.029 5.86 1271 20.40 40.990.014 0.055 9.32 3575 36.24 54.85 0.015 0.030 4.21 1423 19.57 25.870.015 0.034 5.46 1011 22.29 48.44 0.015 0.052 104.20 976 33.96 49.650.015 0.030 4.91 1193 22.68 53.38 0.013 0.033 6.91 1952 29.07 99.270.011 0.042 6.71 2076 37.69 126.30 0.011 Mean: 0.038 16.36 1740 27.6056.92 0.014 Std Dev: 0.010 30.90 776 6.66 31.58 0.002 COV: 27.245 188.8945 24.12 55.48 14.375 10 MM GAUGE LENGTH 0.083 12.82 7201 74.07 58.580.011 0.097 9.58 7090 86.16 59.68 0.011 0.047 8.72 4118 46.20 76.110.010 0.065 11.07 5679 63.58 55.32 0.010 0.053 9.11 4763 51.73 152.600.010 0.044 9.24 34.86 42.78 41.82 0.010 0.068 12.71 6298 66.73 24.520.010 0.028 8.16 1042 21.16 29.46 0.013 0.073 12.27 5664 50.96 39.810.014 0.045 14.23 3591 29.31 9.06 0.015 0.043 11.21 3557 46.80 28.440.009 Mean: 0.059 10.83 4772 52.68 52.31 0.011 Std Dev: 0.020 2.00 184619.01 38.38 0.002 COV: 34.665 18.46 39 36.08 73.37 17.350

[0063] The tenacity measurement of the fibers is reasonably reproducibleconsidering that the equipment is normally used for paper testing. Thetenacity is dependent on the gauge length.

[0064] The dry-jet wet lyocell fibers from the modified unbleached Kraftpulp have a dry tenacity of about 46 cN/tex at a gauge length of 10 mm.If a gauge length of 30 mm is used for testing, the dry tenacity for thelyocell fibers is 30 cN/dtex.

[0065] A decrease in tenacity with increasing gauge length is typical.The result, nevertheless, indicates the potential to produce stronglyocell fibers from modified unbleached Kraft pulps. For example, TITKuses 10 mm gauge length for their testing and usually gives a tenacityof about 35 to 45 cN/tex for dry-jet wet lyocell from bleached pulp.

EXAMPLE 3 Diameter and Lignin Content of Meltblown Lyocell Fiber fromModified Unbleached Pulp

[0066] Using the meltblown spinning system from WTC, lyocell fibers frommodified unbleached Kraft pulp were obtained. The meltblown lyocellfiber had 3.4% of Klason lignin and the diameter results are summarizedin Table 3. TABLE 3 Sample WTC-1 WTC-2 WTC-3 WTC-4 Pulp Acid hydrolyzedunbleached Kraft pulp Throughout/hole (g/m) 2.0 1.0 0.50 0.25 Averagediameter 28.24 20.17 17.62 11.84 (micron) Standard deviation 4.86 2.882.37 1.65 (micron) COV (%) 0.17 0.14 0.13 0.14 Kiason Lignin (%) 34

[0067] As expected, the diameter of the lyocell fiber decreased withdecreasing throughput. The diameter will also be affected by airpressure, temperature, and winder speed, etc. For meltblown lyocellfibers, diameter distribution is usually broader than those from dry-jetwet process. FIG. 12 shows the diameter distribution of meltblownlyocell fiber from modified unbleached Kraft pulp. As can be seen fromFIG. 12, meltblown lyocell fibers with lower average diameter hadnarrower diameter distribution, which is close to that of the dry-jetwet lyocell fibers shown in FIG. 11. Microfibers were produced having adiameter of about 8 microns. Adjusting the process conditions canproduce smaller microfibers. Microfibers have the advantage of providinghigh coverage for various applications.

[0068] While the preferred embodiment of the invention has beenillustrated and described, it will be appreciated that various changescan be made therein without departing from the spirit and scope of theinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method of making alyocell product, comprising: obtaining a pulp having at least 7%hemicellulose, at least 2% Klason lignin, and cellulose, wherein greaterthan 95% of the cellulose of the pulp has an average D.P. of greaterthan 400 to 1100; dissolving the pulp in a solvent to provide acellulose solution; and spinning the cellulose solution into a lyocellproduct.
 2. The method of claim 1, further comprising regenerating thelyocell product in an aqueous regenerating bath.
 3. The method of claim1, wherein the solvent is NMMO.
 4. The method of claim 1, wherein saidmethod is one of at least meltblowing, centrifugal spinning,spun-bonding, and dry-jet wet.
 5. The method of claim 1, wherein saidproduct is one from at least a fiber, a film, and a nonwoven web.
 6. Ameltblowing method for making a lyocell product, comprising extruding acellulose solution of unbleached pulp through a plurality of orifices toproduce continuous cellulose filaments and stretching the filaments withair expelled from said orifices, and finishing said filaments to producesaid lyocell product.